Viscometric Measurement

Both types of instrument commonly have an air bearing to give greater sensitivity with low viscosity samples, although the viscosity of water or simple organic liquids is usually at the lower end of the range. Most instruments would benefit from improvements in thermostatic control. 

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When viscometric measurements of ECH homopolymer fractions were obtained in benzene, the nonperturbed dimensions and the steric hindrance parameter were calculated (24). Erom experimental data collected on polymer solubiUty in 39 solvents and intrinsic viscosity measurements in 19 solvents, Hansen (30) model parameters, 5 and 5 could be deterrnined (24). The notation 5 symbolizes the dispersion forces or nonpolar interactions 5 a representation of the sum of 8 (polar interactions) and 8 (hydrogen bonding interactions). The homopolymer is soluble in solvents that have solubility parameters 6 > 7.9, 6 > 5.5, and 0.2 < <5.0 (31). SolubiUty was also determined using a method (32) in which 8 represents the solubiUty parameter... 

The polymers initiated by BP amines were found to contain about one amino end group per molecular chain. It is reasonable to consider that the combination of BP and such polymers will initiate further polymerization of vinyl monomers. We investigated the photopolymerization of MMA with BP-PMMA bearing an anilino end group as the initiation system and found an increase of the molecular weight from GPC and viscometrical measurement [91]. This system can also initiate the photopolymerization of AN to form a block copolymer, which was characterized by GPC, elemental analysis, and IR spectra. The mechanism proposed is as follows ... 

Modification of filler s surface by active media leads to the same strong variation in viscosity. We can point out as an example the results of work [8], in which the values of the viscosity of dispersions of CaC03 in polystyrene melt were compared. For q> = 0.3 and the diameter of particles equal to 0.07 nm a treatment of the filler s surface by stearic acid caused a decrease in viscosity in the region of low shear rates as compared to the viscosity of nontreated particles more than by ten times. This very strong result, however, should not possibly be understood only from the point of view of viscometric measurements. The point is that, as stated above, a treatment of the filler particles affects its ability to netformation. Therefore for one and the same conditions of measuring viscosity, the dispersions being compared are not in equivalent positions with respect to yield stress. Thus, their viscosities become different. 

Monkos, Karol 2005. A comparison of solution conformation and hydrodynamic properties of equine, porcine and rabbit serum albumin using viscometric measurements. Biochimica et Biophysica Acta 1748,100-109. 

The parameter c can be easily determined by using viscometric measurements, which yield a relative number, or by performing, for example, light scattering measurements, which yield absolute values of c. Viscometric measurements are most commonly used because results are obtained quickly. However, this relative method is not equivalent to the absolute value of c LS and only absolute determination methods such as light scattering result in correct values of c. ... 

Aslam, S. Vossoughi, S. Willhite, G.P. "Viscometric Measurement of Chromium(III)-Polyacrylamide Gels by Weissenberg Rheogoniometer", SPE/DOE paper 12639, 1984 SPE/DOE Fourth Symposium on Enhanced Oil Recovery, Tulsa, April 15-18. 

The conformational mobility of a chromophoric main-chain polymer is often connected to its electronic structure. Therefore, changes in the UV-visible absorption spectra and/or chiroptical properties are spectroscopically observable as thermo-, solvato-, piezo-, or electrochromisms. It is widely reported that o-conjugating polysilanes exhibit these phenomena remarkably clearly.34 However, their structural origins were controversial until recently, since limited information was available on the correlation between the conformational properties of the main chain, electronic state, and (chir)optical characteristics. In 1996, we reported that in various polysilanes in tetrahydrofuran (THF) at 30°C, the main-chain peak intensity per silicon repeat unit, e (Si repeat unit)-1 dm3 cm-1, increases exponentially as the viscosity index, a, increases.41 Although conventional viscometric measurements often requires a wide range of low-dispersity molecular-weight polymer samples, a size exclusion chromatography (SEC) machine equipped with a viscometric detector can afford... 

In order to study the shape of a polymer-Cu complex, viscometric measurements of a homogeneous solution of QPVP were carried out (Fig. 1). At constant QPVP concentration, an increase in the added amount of Cu ions causes a decrease in viscosity, which reveals that the polymer-ligand chain is markedly contracted due to intra-polymer chelation. An intra-polymer chelate takes a very compact form and Cu ions are crowded within the contracted polymer chain (Scheme 2). The adsorption of Cu ions on the polymer ligand is sigmoidal, as can be seen in Fig. 1. At a low... 

Tewari and Srivastava published the results on interaction between atactic polyCvinyl acetate) and poly(acrylonitrile), and poly(methyl methacrylate) and poly(methacrylic acid). On the basis of viscometric measurements of DMF solutions of mixtures of the pair of polymers mentioned above, the authors concluded that for all the systems examined complex formation occurs. This observation explains the results published earlier by the authors about template polymerization of acrylonitrile, methacrylic acid, and methyl methacrylate carried out in the presence of poly(vinyl acetate). It was found that polymerization of acrylonitrile in DMF in the presence of atactic poly(vinyl acetate) (mol. weight 47,900) takes place much faster than without poly(vinyl acetate), especially, when concentration of the monomer is equimolar to the concentration of template repeat units. The overall energy of activation was found to be 55.76 kJ/mol for template polymerization and 77.01 kJ/mol for polymerization in the absence of the template. 

The template polymerization of methacrylic acid at 60 C in DMF was studied with atactic poly(vinyl acetate) M =66,400 used as a template. The effect of template, monomer, and initiator (AIBN) concentration on the kinetics of polymerization was studied dilatometrically. Viscometric measurements showed that complexation between poly(vinyl acetate) and poly(methacrylic acid) was maximized when the template to polymer ratio was 1 1, and for the same ratio of the monomer to the template, the rate of template polymerization also reached the maximum. The overall energy of activation was the same (115 kJ/mol) in the presence and absence of the template. The polymerization follows mechanism II ( pick up mechanism ). 

The only uncertainty about the nature of active centers that remains, concerns their aggregation state. In order to measure the aggregation number, we have performed viscometric measurements on the polymer solutions in benzene, before and after deactivation of the active species. 

The unsuitable nature of many commercial instruments which are in common use clearly illustrates the confusion prevalent in the field of viscometric measurements. Many instruments measure some combination of properties which depend only partly on the fluid consistency since the flow is not laminar. In others the shear rates are indeterminate and the data cannot be interpreted completely. Examples of such units include rotational viscometers with inserted baffles, as in the modified Stormer instruments in which the fluid flows through an orifice, as in the Saybolt or Engler viscometers instruments in which a ball, disk, or cylinder falls through the fluid, as in the Gardiner mobilometer. Recently even the use of a vibrating reed has been claimed to be useful for measurement of non-Newtonian viscosities (M14, W10), although theoretical studies (R6, W10) show that true physical properties are obviously not obtainable in these instruments for such fluids. These various instru-... 

In order to obtain a higher effectiveness of drag reduction, it was therefore more convenient to produce the actual experimental solution from the more diluted stock solution. This is already an indication that the state of solution of macromolecules plays an important role in the interpretation of the results. However, a molecular weight of 10.1 106 g/mol and a concentration of 1000 ppm is just below the critical concentration c (this c is based on viscometric measurements) (Kulicke 1982). Above this critical concentration, mechanical entanglements ensure between the macromolecules. Beneath this limit, interactions between the molecules come into... 

When performing viscometric measurements, the initial concentrations are chosen so as to be less than or equal to c, for light scattering investigations fhey he below c (cf. Fig, 14). It clearly emerges, from a comparison of the defining equations, that all concentrations used for flow measurements lie significantly below these critical... 

Owens, H.S., Lotzkar, H., Schultz, T.H., and Maclay, W.D. 1946. Shape and size of pectinic acid molecules deduced from viscometric measurements. J. Am. Chem. Soc. 68 1628-1632. 

However, Hsieh and Kitchen 151 failed to consider the influence of their measurement temperature, 78 °C, on the stability of the poly(dienyl)lithium active centers (see section on Active Center Stability). As an example of this potential problem is the observation by two separate groups 47-152> that viscometric measurements of hydrocarbon solutions of poly(butadienyl)lithium fail to yield constant flow times (at 30 °C) following the completion of the polymerization, i.e., the flow times were found to increase with increasing time. This inability of the poly(butadienyl)lithium chain to exhibit constant solution viscosities renders it unsuitable for association studies of the type done by Hsieh and Kitchen 151). 

Szwarc and Wang161) have claimed, without citing any supportive experimental measurements, that the equilibrium constant for the process shown in Eq. (11) is approximately one a value in stark contrast to that of ca. 160 LM-1 reported by Morton.42) Their assessment is not supported by the viscometric measurements,42) the kinetic findings of Bywater and Worsfold,156) the association measurements reported by West and Waack56) (Table 3) for benzyllithium in tetrahydrofuran, nor by the findings of Kminek, Kaspar, and Trekoval161a). 

The influence of tetrahydrofuran on the propagation and association behavior of poly(isoprenyl)Iithiura in n-hexane has been examined47. As for the case of poly(styryl)lithium156), the rate of polymerization was found to first increase followed then by a decrease as the THF/active center ratio increased. This decrease ultimately reached the polymerization rate found in pure tetrahydrofuran at a THF active center ratio of ca. 2 x 103. This was for the case where the active center concentration was held constant and the tetrahydrofuran concentration varied. The maximum rate of polymerization was found to occur at a THF active center ratio of about 500 a value at which the viscometric measurements demonstrated 47 the virtual absence of poly(isoprenyl)lithium self-aggregation. As noted before in this review, the equilibrium constant for the process shown in Eq. (12) has the relatively small value of about 0.5 LM-1, which is in sharp contrast with the value of about 160 LM 1 found for the THF-poly(styryl)lithium system. The possibility of complexation of THF directly with the poly(isoprenyl)lithium aggregates, Eq. (13), was not considered by Morton and Fetters47. ... 

The first probable values for the molecular size of the native pectins from apple and sugar beet were obtained by Schneider and co-workers.71 These workers prepared the nitro- and acetyl-derivatives in order to avoid the anomalous behavior due to charge effects which occurred using the unsubstituted polysaccharides. From osmotic and viscometric measurements on the nitrate, values for the molecular weight of 30,000-100,000 were found, the constant Km in Staudinger s equation being 6(10)-4. Viscometric measurements indicated that there was little difference in size between the two derivatives. 

The literature contains numerous observations on the properties of polysaccharides in cuprammonium solutions the work on cellulose is especially voluminous. Viscometric measurements in cuprammonium solution are regularly employed to determine the size of cellulosic molecules. However, before the spatial requirements for complexing with cuprammonium became known the properties of the complexes of polysaccharides could not be interpreted in terms of the structure of their monosaccharide units. With the present understanding of cupram-monium-glycol complexing, some of the earlier observations will be reexamined. 

Methods in which stability can be estimated from the physical degradation of a nitrocellulose gel (viscometric measurements). 

The solutions of PDMS in MEK and CA in mixed solvents were prepared at 313 K during several days. The phase separation temperatures (Tph) for the solutions under shear field and in static conditions were determined by cloud-point method and viscometric. measurements using rotational reometer PVR-2. The spinodal was determined by the light scattering method according to [11. 

The gas phase viscosity is defined by the temperature and the gas composition through a semi-empirical function. For the solid phase shear viscosity, we (cf., 14) use semi-empirical relations based upon the viscometric measurements of Schugerl (21). The solid phase bulk viscosity is, at present, inaccessible to measurement consequently, we define it to be a multiple of the shear viscosity. 

In the determination of the molecular weight of the polymer, sedimentation investigations of its solutions may be replaced by viscometric measurements. It is known 3) a combination of intrinsic viscosity, [n], and diffusion coefficient, D, leads to the equation ... 

However, viscometric measurements of dilute polymer solutions in a steady flow are inadequate for this purpose although, as already indicated, viscosity is related to molecular rotation. This has been demonstrated by Zimm s theory ). Zimm considered the kinetics of the motion and deformation of a kinetically flexible polymer chain in a weak mechanical field with harmonic velocity gradient g at frequency v. It has been found that under steady and weak flow conditions... 

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